Redrawing dies for deep drawing to varying depths



Aug. 3, 1965 J. H. ZEDER, JR 3,197,996

REDRAWING DIES FOR DEEP DRAWING T0 VARYING DEPTHS Filed Dec. 7, 1962 37 A fi 37 m \Km wr Z Q H 1 -30 4 f:562O .6 22' ilz ,24

1 /IO R g IN VEN TOR.

ATTORNEY JOHN H. ZEDER,JR.

United States Patent "ice 3,197,996 REDRAWING DIES FOR DEEP DRAWING T0 VARYING DEPTHS John H. Zeder, Jrz, Southampton, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 7, 1962, Ser. No. 243,066 6 Claims. (Cl. 72-354) This invention relates to a method of deep drawing metal sheets and more particularly to a composite die structure for performing deep drawing, tensioning and flanging of a preformed metal sheet.

In recent years, the automobile industry has adopted the old concept of unitized body construction. This concept requires that the upper balloon or body shell act as a structural support as well as the underbody, permitting the omission of the conventional underframe. It has become the accepted practice in many unitized body constructions to build automobile doors having a thickness approaching nine (9) inches in depth. The outer panel of thedoor is basically a flat sheet formed to the outer contour of the automobile body and having a small turned edge for clinching or attachment to the inner door panel. The inner panel of automobile doors is basically a compound curvature plane bottom connected by deep formed sides on three or more edges terminating in flanges in a compound curvature plane which interconnect and cooperate with the flanges of the door outer panel.

Heretofore, deep formed inner door panels have been made by forming several pieces of sheet metal and welding them together to form an open box having flanged edges. Ordinarily, there would be little difficulty in forming a one-piece rectangular shape similar to a cake pan for the sides do not vary in depth and are very shallow. However, the inner panel of an automobile door requires that the sides vary in depth to match the sculptured flowing design of the outer panel and are deep drawn. Deep drawing of varying depth has inevitably caused buckling or tension failures in the corner edges of the deep draw for metal being pulled into the die cavity is attempting to shrink the peripheral edges of the sheet. It is obvious that an inner door panel deep drawn from a single sheet of metal would be cheaper than fabricating the inner door panel from numerous formed pieces welded together because less equipment, time and material is required in the single piece. The applicant has discovered a novel method and means of deep drawing which permits the fabrication of deep drawn door inner panels from a single continuous flat metal sheet.

The efore, it is a primary object of the present invention to deep form sheet metal objects having compound curvature flanges and varying draw depths throughout the cross section.

It is another object of the present invention to provide composite dies for a novel method of deep drawing metal sheets eliminating several steps formerly employed in deep drawing.

Another object of the present invention is to employ a novel di structure which performs in a single stroke press operation the functions of restraining, tensioning, ironing, drawing, and flange forming.

It is another object of the present invention to provide a method of deep drawing sheet metal objects with control flow of shear deformation and tension deformation to permit consistent results having a superior finish and employing less metal in the blanks.

A preferred embodiment of the die structure employing the principle of deep drawing a preformed metal sheet into a complex-curvature varying-depth deep-draw may in general comprise an upper die plate connected to a 3,197,996 Patented Aug. 3, 1965 movable ram of a press supporting an upper male perimeter die having a vertical extension thereon, a floating upper male die supported by and slidably connected to said upper male perimeter die, a lower female perimeter die mounted on a fixed frame of the press and having vertical extensions thereon, a floating lower die supported on floater pins which pass through said frame and engage a floating platen of a lower cushion cylinder, said floating die being slidably mounted within said lower female perimeter die for vertical movement relative thereto permitting initial movement of said ram to move said die plate, said upper male perimeter die, and said floating upper male die together to first engage said floating upper male die with said floating lower die to entrap said preformed sheet to be deep drawn and continued movement of said rarn subsequently causing the vertical extensions on said upper perimeter die to axially engage an outward extending flange of said preformed sheet to bend over and engage said flange between said vertical extension of said perimeter dies to control and restrain the flow of said metal sheet being deep drawn to varying depth by said upper male dies coacting with said lower dies.

Other features and objects of the invention will be foundthroughout the more detailed description. To more clearly portray the invention and its manner of operation, the description is supplemented with the accompanying drawings wherein:

FIG. 1 is an elevation in section taken through the flange side and lock side of an automobile door die structure just before the die is closed;

FIG. 2 is an elevation in section of the die structure of FIG. 1 at the bottom of the press stroke.

Referring now to FIG. 1 showing a preferred simplified form of the novel die structure adapted to operate in a well known single action press (not shown) having a floating platen. Frame 16 of the press provides a base for attachment of the lower dies. A lower female die 12 mounted on and fixed to the frame 10 is provided with an upward extending vertical portion 14 which serves as a tensioning device or retainer and further provides a seating surface for a preformed sheet 16 to be deep formed. A flanged forming surface 18 and deep drawing surface 2% are also provided on the lower female die 12. A guide surface 22 is provided at the innermost part of the lower female die 12 which serves as a vertical guide for the floating lower die 24. Lower die 24 is floatingly supported on floater pins 25 which engage the well known floating platen of a lower cylinder or cushion ram. These latter parts being well known in the art require no additional explanation. The frame 10 is provided with a cross member 28 which serves as a guide for floater pins 26 and stop means for floating lower die 24. It will be understood that in a normal die forming operation the floating lower die 24 is moved downward against the upward pressure of the floater pins 26 until die 24 engages cross member 28 completing the die forming operation as die 24 bottoms on cross member 28.

Upper male die 30 is fixed to upper die plate 32 which is aflixed to upper platen 34. Upper platen 34 is adapted to be moved vertically by either mechanical or hydraulic means not shown. Upper male drawing die 35 is movable relative to upper die plate 32, as shown, or alternatively, may be fixed for vertical movement with upper male die 39. Movement of upper male drawing die 36 is limited by upper die plate 32 and a die stop 40 on upper male die 30 coacting with stop extensions 42 provided on upper male drawing die 36. Resilient means 37 are provided to urge stop extension 42 of die 36 to engage the die stop 40 of die 30. Such resilient means may be cushions arranged to act similar to pins 26 or may be springs as shown. While it is not necessary to float or spring urge 3 die 36 relative to die 3% such resilient mounting avoids critical tolerances in the dies. 1

FIG. 1 illustrates the simplified die structure with the upper dies in a partially closed position and shows the relative position of the mating face 44 of die 36 relative to the downward extending vertical portions 46. The mating face 44 of die 36 engages preformed sheet prior to the engagement of the downward extending vertical portions 46 of die 36 with the outward extending flanges 48 of preformed sheet 16, thus, enabling the mating faces 4-4 of dies 24 and 36 to clamp the shallow draw bottom 50 of preformed sheet 16 prior to the die forming operation. As die 3% bottoms on die 12 an upper flange forming surface 52 on die 39 engages with the mating flange forming surface 18 on die 12 to form a portion of the outward extending flanges 48 as will be explained hereinafter. Referring now to FIG. 2 showing the die system in closed position, mating faces 44 on dies 24 and 36 clamp or engage the shallow drawn bottom of preformed sheet 16 limiting the forming operation of this portion of the preformed sheet to a restrike operation which does not contemplate any major change in the surface of preformed sheet 16 but merely serves as a clamping operation to pull or deep draw the outward extending flanges 48 into the female die cavity formed by the deep drawing surface 29 on die 12.

Preformed sheet 16 is preferably formed in a conventional set of mating dies to a compound curvature having side walls 54 which are substantially the same depth of draw thus presenting no difficulty employing conventional die drawing practice. However, the outward extending flanges 4 extend outward and upward throughout the cross section of the preformed sheet at varying degrees. The outward extending flange 48 may extend from the side wall 54 horizontally at one portion of the cross section of the preformed sheet while extending outward and upward at an angle of approximately forty-five degrees at another cross section of the preformed sheet 16. Thus, it is understood that the upward extending vertical portions 14 of die 12 and the flange forming surface 18 of die 12 may be of different heights relative to the bottom surface 56 of die 1-2, An important feature of the invention resides in obtaining entirely predictable results in the substantially uniform shallow draw of the preformed sheet and providing the preformed sheet 16 with outward extending flanges which vary in height rel-ative to the bottom of the preformed sheet. Die 12 acts as a lower female perimeter support for at least three sides of the die structure. Die 12 also acts as a tensioning and restraining die which coacts with the vertical extension 46 on die 30. ,Die 12 further acts as a mating and flanging die when flange forming surface 18 coacting with flange forming surface 52 stamps a portion of the outward extending flange 48. The upward extending vertical portions of die 12, while varying in height, form a flush seat for the outward extending flanges 43 of the preformed sheet prior to the novel deep drawing and forming operation.

With preformed sheet 16 seated on the upward extending vertical portions 14 of die 12 the upper dies are lowered to first engage preformed sheet 16 between dies 24 and 36. As dies 30 and 36 move down-ward forcing floater pins 26 downward, the downward extending vertical portions 46 of die 30 engage the outward extending flange 48 substantially simultaneously around the flange 48 bending the outer edge of flange 48 over the outside of upward extending vertical portions 14 of die 12 thus, engaging a portion of flange 48 coaxially between the outer mating surface 58 of die 12 and the inner mating surface 60 of die 30 to bend over and iron out the outer edges of flange 48. Since this is not a shrinking or drawing operation in the outer edges of flange 48 there is no tendency for this portion of the flange to buckle. However, the outer mating surface 58 and inner mating surface 60 coaxially engage the outer edge of flange 48 and iron this surface uniformly fiat as it is pulled into the female cavity of the lower dies removing any imperfections in the sheet. Thus, it is seen that upward extending vertical portion 1 4 of die 12 acts as a restraining (i.e. blank holding) and tensioning device while downward extending vertical portion 46 of die 3% acts as an ironing or straightening die to restrain and tension by blank holding the remaining portion of the metal sheet constituting side walls 54 and outward extending flanges 48. Die 36 acting as a male drawing die also serves as a punch or plug die during the basic drawing operation and restrains the bottom portion of preformed sheet 16 in .its original formed condition without additional tension or shear deformation. As side walls 54 and flanges 48 are drawn between mating surfaces 62 of dies 12 and 36 this portion of the preformed sheet is held in a state of constant tension by extensions 14 and 46 of dies 12 and 35) thus allowing the metal sheet to be deep drawn by shear deformation and uniform tension deep drawing even though the height of the draw may vary throughout the cross-section. Similarly mating surfaces 63 of dies 12 and 36 draw the left hand portion of preformed sheet 16 as shown in FIGS. 1 and 2. Mating surfaces 62 and 63 fully engage only at the bottom of the press stroke whereas mating surfaces at are shown to act coaxially during the press stroke and are disengaged at the bottom of the press stroke. It was found that the deep for-med walls of the inner panel of an automobile door, could be formed deeper with a smaller blank and with varying depth with completely predictable and consistent results which ,is extremely unusual. Further, it was found that the deep draw of varying depth was performed in the edges of the preformed sheet with completely smooth Walls free of buckles and tension tears which occur when deep drawing in varying depths is attempted. Examination of the finished article reveals that the panel has'been deep formed without appreciably thinning the portion of the metal in the side wall of the panel thus indicating that the deep draw has been accomplished wih a maximum of shear deformation and a minimum of tension deformation. This is to say that the outer perimeter of the original sheet has been drawn inward to a smaller width and simultaneously moved in an axial direction without appreciably changing the original thickness of the metal being formed. The results of this deep drawing are further verified by measuring the original surface area and comparing it with the surface area of the final formed sheet showing that deep drawing was accomplished with a negligible change in surface area.

Another feature of the novel die structure permits simultaneously forming flanges at the outer edges of the flange 48. While it is necessary to maintain a tension restraint in the portion of the flange 48 being deep drawn there is no necessity that such conditions prevail for forming the flange portion 64 of flange 48 prior to a trimming operation. As shown in FIG. 2 the flange portion 64 is completely pulled out from between the inner mating surface 64 and the outer mating surface 58 when the flange forming operation occurs thus saving an appreciable portion of metal in the original blank size. It is only necessary that suflicient metal is supplied in the original blank to form the flange portion 64 and allow a slight excess for final trimming. However, it is to be noted that the flanging operation does not require any excess outer edge for holding purposes which is commonly the case in conventional die forming operations. This flanging operation may thus be combined with the deep drawing operation in the novel dies because the bottom surface and deep drawn surface of the sheet 16 are substantially entrapped between the mating surfaces 44, 62 and 63 when the flanging operation occurs. If any analogy is to be made, the drawing dies are now acting as restrainers or restraining dies and the dies which formerly acted as restraining dies are now acting as forming dies.

It is possible to make upward extending vertical portions 14 of dies 12 of constant height on the perimeter and to provide flange forming surfaces 18 of varying height in cross section so that the finished inner panel has a deep draw of varying depth. Such a provision simplifies die construction but requires a larger blank because the blank is then cut for the deepest draw on each side. Extensions 14 of varying height should be employed on high production runs because of material savings.

It is to be understoodthat while a preferred embodiment is shown to explain theprinciple of operation of the novel die structure and the method of forming varying depth deep drawn shapes that modifications and alterations may be made such as reversing the male and female shapes of the dies, and/ or holding the vertical extensions 14 at constant height.

Having described the principle of operation many equivalent structures will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In a die system for deep drawing and flanging a preformed metal sheet having a shallow draw portion and outward extending flange portions comprising in cornbina ti-on, a stationary lower female perimeter die, vertical blank holding dies atfixed on said lower female perimeter die, a floating lower die slidably mounted for vertical movement within said lower female perimeter die, an upper die plate, an upper male drawing die supported by said die plate and adapted to yieldingly engage said floating lower die to entrap said shallow draw portions of said preformed sheet, an upper male perimeter die around said male die, vertical blank holding dies afiixed on said upper male perimeter die cooperating with said vertical blank holding dies affixed on said lower female perimeter die operable to engage in vertical alignment therebetween said flange portions of said preformed metal sheet for yieldingly holding said flange portions when said upper male drawing die deep draws said flange portions into the lower female die, and flange extensions on said perimeter dies intermediate said vertical blank holding dies and said upper male drawing die for forming an offset flange in the outward extending flange portion subsequent to said deep drawing of said flange portion as said metal sheet is held by said upper male die and said lower floating die.

2. A die system for drawing, ironing, forming and flanging in a single press stroke operation a preformed sheet comprising in combination, an upper male perimeter die carried by an upper die plate, said male die having a downward extending forming portion thereon and a lateral extending flanging portion at the outer perim eter thereof, said die being provided with a vertical and downward extending blank holding and ironing portion and a lateral and downward extending stop guide portion, an upper male drawing die carried by said lateral and downward extending stop guide portion of said upper male perimeter die, yielding means urging said upper male drawing die into engagement with said stop guide portion of said perimeter die, a lower female perimeter die carried on a fixed frame, said lower female perimeter die having a lateral extending flanging portion, a substantially vertical deep drawing portion, and a vertical upward extending blank holding and ironing portion adapted to entrap the outward extending edges of said preformed sheet between said vertical extending blank holding and ironing portions, simultaneously ironing and restraining the flow of said preformed sheet into said lower female perimeter die, a lower floating die carried on yielding pilot pins, said lower die being vertically guided by said lower female perimeter die, and means for engaging the upper dies upon the preformed sheet positioned by the lower dies whereby said preformed sheet is first deep formed between said upper male die and said lower female die while said vertical extending blank holding portions on said perimeter dies retain tension in the edges of said preformed sheet, said edges being flanged and formed by said perimeter dies during the final closing of the die system after deep drawing of the edges of said preformed sheet.

3. In a die system for deep forming from a preformed sheet having outward extending flanges automobile door inner panels, deep drawn to varying depths, a movable upper die plate supporting an upper male perimeter die having at the outer perimeter thereof a vertical, blank holding extension, varying in height thereon, a floating upper male drawing die supported by and slidably connected to said upper male perimeter die, a lower female perimeter, drawing die mounted on a fixed frame of a press and having a vertical blank holding extension varying in height and aligned in a vertical plane parallel to the other said vertical blank holding extension thereon, a floating lower die supported on pilot pins which pass through said frame and engage a floating platen of a lower cushion cylinder, said floating die being slidably mounted within said lower female perimeter drawing die for vertical movement relative thereto whereby relative downward movement of said upper die plate engages the flat center portion of a preformed sheet between said upper male die and said lower floating die and moves said sheet and said lower floating die downward causing outward extending flanges of said preformed sheet to be bent over and aligned vertically between said vertical blank holding extensions of said perimeter dies to control and restrain the flow of said metal sheet being deep drawn to varying depths by said upper male dies coacting with said lower dies.

4. In a die system for deep forming a preformed metal sheet having a shallow drawn bottom and an outward extending flange edge shaped to a compound curvature comprising in combination; a lower female forming die adapted to fold, tension, and form said outward extending flange, said lower female die having an upward ex tending blank holding vertical portion varying in height and forming a perimeter support juxtaposed said compound curvature of said flange edge said outward extending flange; a lower floating die providing a seat for said shallow drawn bottom; an upper male drawing die having a mating face matching said lower floating die for engaging said shallow drawn bottom of said preformed metal sheet therebetween; and an upper male forming die adapted to simultaneously engage and fold said outward extending flange edge over the outside of said upward extending vertical blank holding portion of said lower female forming die to tension and restain said outward extending flange while said upper male drawing die deep draws said flange into the female cavity of said lower female forming die.

5. A system of redrawing dies for deep drawing to varying depths a preformed sheet having a shallow drawn bottom and outward extending edges, said edges having a compound curvature representative of varying height at the outward extending edges, comprising in combination:

(a) a lower female forming die adapted to fold, tension and form said outward extending edges, comprising;

(l) a female deep drawing portion,

(2) an upward extending vertical blank holding portion connected to said female deep drawing portion, having (3) a preformed sheet edge supporting face engageable with the bottom of said outward extending edges, and

(4) a vertical blank holding tension face;

(b) a lower floating die provided with a seat engageable with said shallow drawn bottom of said preformed sheet;

(0) an upper male drawing die adapted to clamp said shallow drawn bottom and deep draw said outward extending edges, comprising:

(1) a clamping portion cooperable with said lower floating die, a (2) a male deep drawing portion cooperable with a female deep drawing portion;

(d) an upper male perimeter die adapted to fold, tension and form said outward extending edges, comprising: a

(1) a preformed sheet edge folding face engageable with the top of said outward extending edges and c'ooperable with said edge supporting face of said upward extending vertical portion of said lower female forming die to fold said edges over and in axial alignment with said vertical blank holding tension face, and

(2) a vertical tension face cooperable with said vertical blank holding tension face on said lower female forming die to control andlrestrain the flow of metal into said female deep drawing portion of said female forming die.

6. A die system according toclaim 5 wherein said lower female forming die and said upper male forming die are further provided with mating horizontal flange sur 8 faces varying in heightfor forming the extending edges of said preformed sheet which had been folded over outside of said upward extending vertical blank holding portion and drawn into said lower female forming die by said upper male drawing die.

References Cited by the Examiner UNITED STATES PATENTS 851,630 4/07 Sloman 11346 2,136,308 11/38 Miller i 113-49 2,689,539 9/54 Lyon 113-49 2,735,390 2/56 Engel 113-51 2,751,872 6/56 Hodes 11346 2,771,851 11/56 McGregor 11346 2,899,922 8/59 Wheeler 11349 2,921,548 1/60 Lyon 113--49 3,000,274 9/61 Duskey et al. 113-49 3,016,853 1/62 Celovsky 113-49 3,056,367 10/62 Lyon 113-51 3,163,142 12/64 Buhrke 113-45 CHARLES W. LANHAM, Primary Examiner.

NEDWIN BERGER, Examiner. 

1. IN A DIE SYSTEM FOR DEEP DRAWING AND FLANGING A PREFORMED METAL SHEET HAVING A SHALLOW DRAW PORTION AND OUTWARD EXTENDING FLANGE PORTIONS COMPRISING IN COMBINATION, A STATIONARY LOWER FEMALE PERIMETER DIE, VERTICAL BLANK HOLDING DIES AFFIXED ON SAID LOWER FEMALE PERIMETER DIE, A FLOATING LOWER DIE SLIDABLY MOUNTED FOR VERTICAL MOVEMENT WITH SAID LOWER FEMALE PERIMETER DIE, AN UPPER DIE PLATE, AN UPPER MALE DRAWING DIE SUPPORTED BY SAID DIE PLATE AND ADAPTED TO YIELDINGLY ENGAGE SAID FLOATING LOWER DIE TO ENTRAP SAID SHALLOW DRAW PORTIONS OF SAID PREFORMED SHEET, AN UPPER MALE PERIMETER DIE AROUND SAID MALE DIE, VERTICAL BLANK HOLDING DIES AFFIXED ON SAID UPPER MALE PERIMETER DIE COOPERATING WITH SAID VERTICAL BLANK HOLDING DIES AFFIXED ON SAID LOWER FEMALE PERIMETER DIE OPERABLE TO ENGAGE IN VERTICAL ALIGNMENT THEREBETWEEN SAID FLANGE PORTIONS OF SAID PREFORMED METAL SHEET FOR YIELDINGLY HOLDING SAID FLANGE PORTIONS WHEN SAID UPPER MALE DRAWING DIE DEEP DRAWS SAID FLANGE PORTIONS INTO THE LOWER FEMALE DIE, AND FLANGE EXTENSIONS ON SAID PERIMETER DIES INTERMEDIATE SAID VERTICAL BLANK HOLDING DIES AND SAID UPPER MELE DRAWING DIE FOR FORMING AN OFFSET FLANGE IN THE OUTWARD EXTENDING FLANGE PORTION SUBSEQUENT TO SAID DEEP DRAWING OF SAID FLANGE PORTION AS SAID METAL SHEET IS HELD BY SAID UPPER MALE DIE AND SAID LOWER FLOATING DIE. 